795 research outputs found
Fast and accurate simulations of transmission-line metamaterials using transmission-matrix method
Recently, two-dimensional (2D) periodically L and C loaded transmission-line
(TL) networks have been applied to represent metamaterials. The commercial
Agilent's Advanced Design System (ADS) is a commonly-used tool to simulate the
TL metamaterials. However, it takes a lot of time to set up the TL network and
perform numerical simulations using ADS, making the metamaterial analysis
inefficient, especially for large-scale TL networks. In this paper, we propose
transmission-matrix method (TMM) to simulate and analyze the TL-network
metamaterials efficiently. Compared to the ADS commercial software, TMM
provides nearly the same simulation results for the same networks. However, the
model-process and simulation time has been greatly reduced. The proposed TMM
can serve as an efficient tool to study the TL-network metamaterials.Comment: 15 pages, 13 figure
Many-body Chemical Reactions in a Quantum Degenerate Gas
Chemical reactions in the quantum degenerate regime are described by mixing
of matterwave fields. Quantum coherence and bosonic enhancement are two unique
features of many-body reactions involving bosonic reactants and products. Such
collective reactions of chemicals, dubbed "super-chemistry", is an elusive goal
in quantum chemistry research. Here we report the observation of coherent and
collective reactive coupling between Bose condensed atoms and molecules near a
Feshbach resonance. Starting from an atomic condensate, the reaction begins
with a rapid formation of molecules, followed by oscillations of their
populations in the equilibration process. Faster oscillations are observed in
samples with higher densities, indicating bosonic enhancement. We present a
quantum field model which describes the dynamics well and identifies three-body
recombination as the dominant reaction process. Our findings exemplify the
highly sought-after quantum many-body chemistry and offer a new paradigm for
the control of quantum chemical reactions.Comment: 15 pages, 10 figures. Nat. Phys. (2023
Controlling Frequency-Domain Hong-Ou-Mandel Interference via Electromagnetically Induced Transparency
Hong-Ou-Mandel (HOM) interference is a compelling quantum phenomenon that
demonstrates the nonclassical nature of single photons. Herein, we investigate
an electromagnetically induced transparency-based double-Lambda four-wave
mixing system from the perspective of quantized light fields. The system can be
used to realize efficient HOM interference in the frequency domain. By using
the reduced density operator theory, we demonstrate that, although the
double-Lambda medium does not exhibit phase-dependent properties for the
closed-loop case of two incident single photons, frequency-domain HOM
two-photon interference occurs. For experimentally achievable optical depth
conditions, our theory indicates that this double-Lambda scheme can perform
high-fidelity Hadamard gate operations on frequency-encoded single-photon
qubits, and thereby generate HOM two-photon NOON states with a fidelity greater
than 0.99. Furthermore, we demonstrate that this scheme can be used to realize
arbitrary single-qubit gates and two-qubit SWAP gates by simply controlling the
laser detuning and phase, exhibiting its multifunctional properties and
providing a new route to scalable optical quantum computing.Comment: 10 pages, 5 figure
High-brightness switchable multi-wavelength remote laser in air
Remote laser in air based on amplified spontaneous emission (ASE) has
produced rather well-collimated coherent beams in both backward and forward
propagation directions, opening up possibilities for new remote sensing
approaches. The remote ASE-based lasers were shown to enable operation either
at ~391 and 337 nm using molecular nitrogen or at ~845 nm using molecular
oxygen as gain medium, depending on the employed pump lasers. To date, a
multi-wavelength laser in air that allows for dynamically switching the
operating wavelength has not yet been achieved, although this type of laser is
certainly of high importance for detecting multiple hazard gases. In this
Letter, we demonstrate, for the first time to our knowledge, a harmonic-seeded
switchable multi-wavelength laser in air driven by intense mid-infrared
femtosecond laser pulses. Furthermore, population inversion in the
multi-wavelength remote laser occurs at an ultrafast time-scale (i.e., less
than ~200 fs) owing to direct formation of excited molecular nitrogen ions by
strong-field ionization of inner-valence electrons, which is fundamentally
different from the previously reported pumping mechanisms based either on
electron recombination of ionized molecular nitrogen or on resonant two-photon
excitation of atomic oxygen fragments resulting from resonant two-photon
dissociation of molecular oxygen. The bright multi-wavelength laser in air
opens the perspective for remote detection of multiple pollutants based on
nonlinear spectroscopy.Comment: 18 pages, 5 figure
bioPrint: A Liquid Deposition Printing System for Natural Actuators
This article presents a digital fabrication platform for depositing solution-based natural stimuli-responsive material on a thin flat substrate to create hygromorphic biohybrid films. Bacillus subtilis bacterial spores are deposited in the printing process. The hardware system consists of a progressive cavity pump fluidic dispenser, a numerical control gantry, a cooling fan, a heating bed, an agitation module, and a camera module. The software pipeline includes the design of print patterns, simulation of resulting material transformations, and communication with computer hardware. The hardware and software systems are highly modularized and can therefore be easily reconfigured by the user
A huge traumatic pulmonary pseudocyst
AbstractTraumatic pulmonary pseudocyst (TPP) is a rare complication following blunt trauma. We report a 26-year-old male patient who presented to the emergency room with internal bleeding and shock. Huge TPP (14Â cm in diameter) was seen on whole-body computed tomography scan and complicated with bronchial bleeding. He deteriorated to respiratory failure soon after arriving at the emergency room. TPPs imply high-energy impact on the chest region and frequently complicated with pulmonary contusions, hemo- and pneumo-thorax, multiple rib fractures, flail chest, and concurrent with abdominal injuries. Emergency physicians should be aware of such rare entity and manage correctly
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